1. Technical Field of the Invention
The present invention relates generally to a sequentially joined-segment armature and an ac machine using the same which may be employed as a rotary electric machine for automotive vehicles.
2. Background Art
Idle stop systems, as having been employed in automotive vehicles in recent years, are designed to perform frequent engine start-and-stop operations, therefore, use of ac motors is preferable to dc motors with brushes. However, ac motors capable being supplied with a great starting current equivalent to that use in typical dc series-wound motor will be greater in size than typical alternators, thus requiring a large amount of space within an engine compartment of the vehicles or a substantial change in engine layout, which may lead to an increase in weight of the vehicles.
As automotive ac generators, ac machines have been proposed which are equipped with a conductor segment-joined armature made up of U-shaped conductor segments which are disposed within slots formed in a stator core and joined sequentially. For instance, Japanese Patent First Publication Nos. 11-164506 and 2001-169490 disclose such a type of ac machine.
Japanese Patent First Publication No. 2001-169490 (corresponding to U.S. Pat. No. 6,417,592 B2 to Nakamura et al. assigned to the same assignee as that of this application) discloses segment-joined automotive ac generator which is equipped with U-shaped large-sized conductor segments and U-shaped small-sized conductor segments which partially extend through slots arrayed in a stator core in a circumferential direction thereof. Each of the slots has a first, a second, a third, and a fourth layer positions arrayed from inside to outside of the stator core in a radius direction thereof. The large-sized conductor segments each have legs disposed in the first and fourth layer positions of the slots. The small-sized conductor segments each have legs disposed in the second and third layer positions of the slots. A total of four turn coils, two disposed in two of the slots located across one of the slots, are so connected as to cross to joint two of the turn coils in parallel to make phase windings. Specifically, an eight conductor-in-two slot stator coil is taught to double the current permitted to be supplied to the coil without increasing poles.
Japanese Patent First Publication No. 11-164506 teaches a six conductor-in-one slot stator coil which is equipped with U-shaped large-sized conductor segments and U-shaped small-sized conductor segments which partially extend through slots arrayed in the stator core in the circumferential direction thereof. Each of the slots has a first, a second, a third, a fourth, a fifth, and a sixth layer positions arrayed from inside to outside of the stator core in the radius direction thereof. The large-sized conductor segments each have legs disposed in the first and sixth layer positions of the slots. Some of the small-sized conductor segments have legs disposed in the second and third layer position of the slots. The others have legs disposed in the fourth and fifth layer positions of the slots. This structure permits the number of turns of the stator coil to be five times greater than that disclosed in the former publication, thus providing a high-voltage stator coil.
The above described stator coils are designed to fix a wiring pattern or order of joints of the conductor segments. It is, thus, difficult to increase the turns of the stator coil without increasing rotor poles, thereby increasing a difficulty in using the rotary machine with a high-voltage battery in automotive vehicles. Further, increasing a sectional area of the conductor segments results in a difficulty in bending thereof, which increases a difficulty in use of the stator coil with a great current.
Locations where lead wires extend from the parallel-connected phase windings of each of the phase coils are greatly away from each other, thus resulting in an increase in length of the lead wires, which leads to increased resistance and inductance of the lead wires. The increase in length of the lead wires also requires a large amount of space in the rotary machine, thus resulting in an increased length of the rotary machine.